Recording heads, such as magnetoresistive (MR) heads, are typically formed of various layers deposited upon a substrate. MR heads utilize a MR element or sensor positioned between a top shield (TS) and a bottom shield (BS) to read magnetically-encoded information from a magnetic medium, such as a disc, by detecting magnetic flux stored on the magnetic medium. The MR sensor has a proximal end and a distal end, with the proximal end of the MR sensor forming a portion of an air bearing surface (ABS) of the head. In one type of MR head, a sensing current for detecting magnetic bits of information passes in a plane of the MR read element. Such a MR head is referred to as a Current-In-Plane (CIP) Spinvalve transducer. A ferromagnetic stabilization scheme for traditional CIP Spinvalve transducers utilizes permanent magnets (PM), positioned proximate the ABS of the head on either side of the MR sensor, which essentially define the MR sensor's reader width. The transducer is operated by running an electrical current from one PM to the other after passing through the MR sensor.
A recently developed so-called CIP Trilayer Spinvalve transducer, however, places the stabilizing PM material behind the distal end of the MR sensor within the slider body, with the PM material being separated from the distal end of the MR sensor by a dielectric layer. Typically, the dielectric layer is thin enough to provide the proper amount of magneto-static coupling to the MR sensor for magnetic stabilization but thick enough to prevent electrical current from shunting through the PM material and thereby reducing the MR signal during read operations. The CIP Trilayer Spinvalve sensor defines its reader width with non-magnetic extended contacts (EC) and the sense current flows from one EC to the other after passing through the MR sensor.
This ferromagnetic stabilization scheme employed in the so-called CIP Trilayer Spinvalve transducer creates a risk of Reader-to-Permanent Magnet Isolation (RPM-Iso) failure. If RPM-Iso failure is present, then electrical current which ordinarily travels through the MR sensor for detecting magnetic bits of information on the recording medium can shunt through the PM material and reduce the MR response, thereby resulting in a defective transducer.
Traditional CIP Spinvalve transducers and CIP Trilayer Spinvalve transducers incorporate a shield-shunt connection which electrically connects the BS to the TS. The shield-shunt connection can be used for Reader-to-shield Isolation (RS-Iso) failure testing to detect defective transducers. However, as mentioned above, the ferromagnetic stabilization scheme employed in the CIP Trilayer Spinvalve transducer also creates a risk of RPM-Iso failure.
Thus, the need for a scheme for testing CIP Trilayer Spinvalve transducers for the presence or absence of proper RPM-Iso.